Most photographic film now used is 35 mm format film. Cameras have been developed to allow film of this format to be easily loaded by placing the film cassette, in which the film is stored, into an opening in the back of the camera and then shutting the back of the camera. As a free end or tongue of the film extends externally to the film cassette, this is used to automatically advance the film in the camera for picture taking. Once all the pictures have been taken, the film is rewound into the film cassette for removal from the camera for processing. In order for this to work, the free end or tongue of the film must extend externally to the cassette so that it can be pulled on to the take-up spool in the camera as the film is first loaded.
Photographic film tends to be processed in a single strip once the film has been removed from its cassette. Strips of negative film are processed by transporting them, either as a single individual strip or as a continuous length comprising two or more strips of shorter lengths, through a series of processing solutions in various tanks in the processing apparatus.
In known processing apparatus, the film strip is pulled through tanks containing the processing solutions either by a leader which is attached to the leading edge of the film strip, or by moving a rack or spiral containing the film strip from tank to tank. Individual film strips may be pre-spliced into a long reel with a leader card at the front end, clipped to a rack, or fed into a spiral.
Where the film strip is attached to a leader, it is unloaded from the cassette and attached to the leader in a manual operation. The leader is then fed into the processing apparatus so that the film can be processed as it is transported through the apparatus.
Operations of splicing the film strips together or attaching the leader to the strip need to be carried out in darkroom conditions due to the sensitive nature of the film.
As an alternative to providing a leader for the film strip, the leading edge of the film may be used as a leader to guide the strip through the processing apparatus. However, this may cause problems as the leading edge of the film may have become damaged during loading and/or unloading of the film into and out of the camera.
It is therefore one object of the present invention to is provide a leaderless arrangement for transporting a film strip through processing apparatus. This is achieved by utilizing a guillotine which cuts the film strip from its supporting spool after it has been fully unwound therefrom.
Guillotine blades are well known for a variety of applications. However, most of these blades are rigid and are substantially planar and have a planar cutting edge. Rigid guillotine blades have the disadvantage that they cannot be used in confined spaces.
U.S. Pat. No. 3,777,609 discloses a trimming device which is used to trim the bottom of hollow plastic bodies after they have been fabricated using extrusion blow moulding techniques. The trimming device includes a movable flexible blade, a mechanism for effecting periodic displacement of the blade and a slide guide which guides the blade during its displacements. The slide guide comprises at least one metal guide which is fixed to the bottom of the mould and which causes the blade to follow the shape at the bottom of the mould during its displacements. The blade is curved to have a shape which is intermediate that of the bottom of the mould and its trajectory outside of the slide guide. In operation, the blade is reciprocated between two positions, a rest position and an operative position.
This arrangement requires complicated linkages to allow the blade to be moved from its rest position to its operative position and back again during the return stroke.
It is therefore a further object of the present invention to provide a movable flexible guillotine blade which overcomes the disadvantages of known flexible guillotine blade arrangements.